Printer feed speed control



Jan. 6, 1970' E; NEL-59N ETAL 3,487,986`

PRINTER FEED SPEED coNTEoL Filed Feb. 20, 1968 United States Patent O 3,487,986 PRINTER FEED SPEED CONTROL Earl L. Nelson, Lake Park, and Robert C. Peyton, North Palm Beach, Fla., assignors to RCA Corporation, a corporation of Delaware Filed Feb. 20, 1968, Ser. No. 706,808 Int. Cl. B65h 23/22, 25/00 ILS. Cl. 226-42 3 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION The use of modern high-speed printers has introduced a serious problem in handling the large amount of the printed recording strip which they issue during their highspeed strip feed mode. This recording strip is customarily arranged to be folded or stacked at a stacking station to produce a compact printed record storage. To Ialleviate this problem, contemporary printer systems are equipped with paper pullers located bet-Ween the printing station and the stacking station. These pullers perform two functions; namely, they limit the maximum input rate to the stacker to a rate which the stacker can handle, and they provide a means for positively transporting the record medium to the stacking station.

Under the usual operation of prior printer systems, the average output rate of the printing station in the slow feed mode is slower than the puller rate, and the recording medium strip is maintained under tension between the two units, with tearing of the strip being prevented by slippage at the puller. However, during an operating mode in which little printing is effected but a considerable amount of advance of the strip is desired, the printer is operated in the high speed feed mode, which exceeds the capacity of the puller `and produces an excess of slack recording strip between the two units with possible consequent damage to the strip and jamming of the system. This problem is accentuated in a contemporary printer system enclosed in tight tting covers which provide a minimum of space for such strip excess. Accordingly, it is desirable to provide a printer system having means for automatically limiting the slack strip length while achieving an operativ-e compatibility between the printer and puller.

BRIEF SUMMARY OF THE INVENTION DETAILED DESCRIPTION Referring to the drawing, there is shown an embodiment of the present invention for use as a speed control for a printer recording medium feed system. A supply roll 1 is mounted on any suitable means (not shown) to supply a recording medium, e.g., a continuous paper strip 2, to a printer 3. In the illustrated embodiment, the strip 2 would be a wide paper sheet having transverse perforations at regular intervals which allow the strip 2 to be folded and stored by a puller and stacker 5 into a receiving bin 7. During the passage of the strip 2 between the printer 3 `and the stacker 5, a slack open loop 8 is maintained to allow for the operational discrepencies between the printer 3 and the stacker 5. In other words, the loop 8 is effective to allow the stacker 5 to proceed at a preset speed while the printer 3 is switched between a high speed feed mode and a low speed feed mode, with a consequent variation in the speed of the strip 2 issuing from the printer 3. In order to maintain an optimum relationship between the speeds of the printer 3 and the stacker 5, it is desirable to maintain the loop 8 at a pre- The illustrated embodiment of the invention is a speed y BRIEF DESCRIPTION OF THE DRAWING In the accompanying drawing there is shown a block diagram of a printer feed speed control system embodying the present invention.

determined length.

The system shown in the drawing provides a variable speed energizing signal to a printer line advance drive 9 and a fixed speed control signal to the puller and stacker 5. A drive control means 10 is connected to the printer drive 9 by a speed control signal line 11 and to the stacker 5 by a control signal line 12. A mode select control 14 is connected to the drive control 10 by two signal lines 16, 17 which are labeled stop and slow, respectively. The lines 16, 17 supply control signals to the dri-ve control 10, which signals are selected by `an operator actuating the mode `control 14 by any suitable means, e.g., push-button switches. Alternatively these signals may be supplied from a computer (not shown) under program control. A third control 18, labeled fast, is connected to one input of a tirst AND gate 20. A second input of the AND gate 20 is connected as hereinafter described. The output of the AND gate 20 is connected to a third input of the drive control 10.

The drive control 10 produces a discrete advance output signal on an advance output line 22 representative of each incremental movement of the strip 2 through the printer 3 for both the fast and slow modes. The ad- Vance line 22 is connected to forward count input of a suitable bidirectional counter 24. An output signal from a clock 27 is applied to one input of a second AND gate 29. The output of the second gate 29 is applied to a reverse count input of the counter 24. A comparator 31 is connected to the counter 24 to sense the count therein and to compare this count with the preset maximum count limit stored in a limit store means 32. A low output line 33 from the comparator 31 is connected to the reset input of `a flip-flop 35. A high output line 37 from the comparator 31 is connected to a set input of the flip-Hop 3S. Additionally, a second output line 40 from the counter 24 is connected to a second input of the second gate 29 to supply a signal representative of a count in the counter 24 other than zero. The 0 output of the ip-flop 35 is connected by a line 42 to a second input of the first gate 20.

In operation, the system illustrated maintains the length of the loop 8 approximately at the predetermined limit preset in the limit store 32. This control is achieved by driving the printer line advance drive 9 at either a high or a low speed lwhile the puller and stacker 5 are driven at a preset speed. The line advance speed of the strip 2.

through the printer 3 is represented by a train of discrete signals on the advance line 22 from the drive control 10. Thus, the strip 2 is incrementally advanced through the printer v3 each line by the drive control 10 at a speed determined `by the mode select control 14 and the control-system hereinafter described.-

The signals on line 22 are. applied to the forward -count input of the counter 24 to advance the count stored therein. The xed frequency signals from the clock 27 are applied to the backward count input of the counter 24 to decrease the count stored therein. The frequency of the clock signals is selected to represent the pulling and stacking sped of the stacker 5, i.e., each signal from the clock 27 represents one print line moved by the stacker 5. It should be noted that the illustrated system could be modied by replacing the clock 27 with an oscillator means driven by the puller and stacker 5 without departing from the scope of the present invention. The resulting `count in i the counter 24, accordingly, represents the difference be# tween the print lines issued by the printer and the print lines handled by the stacker 5. This resulting count is monitored by the comparator 31 and compared with a preset limit count from the limit store 32.

In an initial state of a zero count in the counter 24, the output signals from the clock 27 are blocked by the gate 29 since this gate is controlled by an output signal from the counter 24 on line 40. The level of this output signal when it is representative of a count in the counter 24 greater than zero is eiiective to open the gate 29. Thus, whenever a zero count is stored in the counter 24, only the advance signals on line 22 are applied to the counter 24 to increase the stored count.

The comparator 31, also, produces a pair of output signal levers on respective output lines 33 and 37, which signal levels are applied to the reset and set inputs, rcspectively, of the flip-flop 35 to aiect the llip-llop output levels. Specifically, the signal level on input lines 33, which is representative of a monitored count which is lower than the preset limit, places the ip-op 35 in a reset state wherein the 0 output of the ip-op 35 opens the gate 20. Conversely, the signal level on input line 37 representative of a monitored count which is higher than the preset limit, places the ilip-ilop 35 in a set state wherein the O output level closes the gate 20. The gate 20 controls the application of the fast mode signal from the mode select means 14 to the drive control 10. Thus, when the gate 20 is open, the fast mode signal is applied to the drive control 10. This mode signal overrides the normally applied slow mode signal on line 17 to actuate the drive control to produce a fast drive signal on line 11 for the printer drive 9.

On the other hand, when the gate 20 is closed, kthe fast mode signal is blocked, and the printer line drive 9 is driven at a slow speed by the drive control 10. Since the gate 20 is controlled by the output signals from the comparator 31, the printer line drive 9 is driven at a high speed when the stored count in the counter 24 is lower than the preset limit count and is driven at a slow speed when the count in counter 24 is higher than the preset limit.

Starting from the initial state of the illustrated system, the count in the counter 24 would be zero and the strip 2 is fed into the stacker 5 with no substantial loop 8 in the strip 2. Since the count in the counter 24 would, at this time, be below the count limit, the iiip-op 35 is reset by the signal on` line 33 from the comparator 31, which state of the ip-op l35 opens the gate 20. As a result, the fas mode signal from the mode select control 14 can be applied to the drive control 10. Thus, the printer line drive 9 can be initially driven at either a slow or a fast speed depending on whether normal printing or a rapid line advance is desired, respectively. As soon as the drive control 10 starts to drive the paper through the printer 3, the line advance signals on line 22 are' applied to advance the count inthe counter 24. If only valslow mode operationforV the printer -line drive 9is used,the

count in the counter 24 is not advanced since the clock signals are equal to or greater than the slow line advance rate. However, if a fast line advance rate is desired, the fast drive signal is applied to the drive control 1Y0 which drives the printer" line advance drive 9 at a fast speed.

When the stored count is greater thanvzero, as a `result of a continued fast mode, the gate 29 is opened by the signal level on line'40to allow the signals from the clock 27 to be applied to the counter 24 to decrease the stored count. Since in the fast mode,l the printer line drive 9 operates at a higher speed than the stacker 5, the loop 8 is established-and gradually increased in length. This increase in loop length isrepresented by a count increase inthe counter 24 `since the clock signals are slowerthan the fast, advance signals. The loop length is increased until `the stored, count is greater than the limit count pref setin the limit store 32. At this time, the ip-flop is set by the output level on line 37 from the comparator 31. This state of the ip-flop 35 terminates the gate actuating level to the gate 20 and closes the gate 20. The fast mode signal to the drive control 10 is blocked by the unenergized gate 20, and the printer line drive '9 is driven at a lslow speed by the dominant slow mode signal applied to the drive control 10. Since the clock signals are faster than the advance signals for the slow printer speed, the countin the counter 24 is restored to a count lower than the limit count, `and the flip-flop 35 is reset by the comparator 31. The reset state ofthe ip-flop 35 reopens the gate 20, and the printer li'ne drive 9 can, again, be driven at a high speed. This alternate operation of the printer 3 line feed 9 duringv a fast line advance mode is successively repeated by the continued transitions of the stored count above and below the limit count. As a result of this operation, the loop 8 is maintained at the desired v length.

What is claimed is:

1. A speed control for a moving strip comprising means operative to compare the advance rate of said strip at two spaced points in a'strip drive system and to produce an output signal representative of the difference therebetween, means for comparing said difference with a preset limit for said dilerence, and means responsive to said means for comparing to maintain the length of an open loop of said strip between said points at a value represented by said limit by controlling the speed of said strip at one of said points. 4 A

`2. A speed controlas lset forth in claim 1 and including a strip recording means and a strip storage means, wherein said twovpoints are respectively located at the output of said strip recording means and at the output of said storage means handling said strip after printing. K' 3. A speed controlas set forth in claim 1 wherein said means responsive includes means for switching the speed of said/ strip between a low speed and a high speed in ref. sponse to said difference being higher than said limitand to said difference being lower than said limit, respectively.

v References Cited o UNITED STATES PATENTS 

